首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   19902篇
  免费   291篇
  国内免费   187篇
安全科学   732篇
废物处理   623篇
环保管理   3553篇
综合类   4048篇
基础理论   4817篇
环境理论   19篇
污染及防治   4801篇
评价与监测   1026篇
社会与环境   626篇
灾害及防治   135篇
  2022年   131篇
  2021年   143篇
  2019年   162篇
  2018年   289篇
  2017年   313篇
  2016年   419篇
  2015年   315篇
  2014年   423篇
  2013年   1528篇
  2012年   617篇
  2011年   849篇
  2010年   595篇
  2009年   718篇
  2008年   794篇
  2007年   854篇
  2006年   747篇
  2005年   581篇
  2004年   589篇
  2003年   615篇
  2002年   522篇
  2001年   592篇
  2000年   442篇
  1999年   324篇
  1998年   251篇
  1997年   231篇
  1996年   267篇
  1995年   286篇
  1994年   297篇
  1993年   266篇
  1992年   262篇
  1991年   238篇
  1990年   260篇
  1989年   238篇
  1988年   200篇
  1987年   212篇
  1986年   204篇
  1985年   216篇
  1984年   203篇
  1983年   220篇
  1982年   229篇
  1981年   224篇
  1980年   190篇
  1979年   171篇
  1978年   170篇
  1977年   149篇
  1976年   156篇
  1975年   129篇
  1974年   153篇
  1973年   128篇
  1972年   135篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
381.
This article reports the results of a retrospective study designed to examine the responses of couples to genetic amniocentesis and subsequent therapeutic abortions due to birth defects. Fourteen women and 12 men were interviewed by experienced interviewers using a structured format designed by the authors, and each interview was audiotaped for later rating. The 5 raters (all women) were instructed to independently rate each interview using forms designed by the authors to elicit information about many aspects of the participant's individual responses as well as perceptions of spouse's responses to the process of pregnancy, amniocentesis, therapeutic abortion, and sequelae. Ratings of all 5 raters were conjoined and an homogeneous narrative was constructed for each interview. Results indicate, in general, that the respondent couples coped well with this experience. In fact 70 per cent of the respondent couples described their marital relationships as becoming closer as a result of their experience. Only a few participants reported long-term deleterious effects. Most couples coped by relying on relatives, friends, and occasionally, professional counsellors. In addition, most participants in this study suggested ways to improve the medical and psychological aspects of this experience.  相似文献   
382.
Our understanding of amorphous semiconductors has been greatly clarified by recent theoretical and experimental work. It is now evident that the electrical properties of these materials are generally controlled by intrinsic defects which are either thermodynamically required or induced via strains during the deposition process. The nature of these defects is intimately related to the chemistry of the constituent atoms.  相似文献   
383.
The role of the development of information fidelity systems in evolution is explored, with evidence that the loss in the ability to maintain the integrity of homeostasis in organisms over time, aging, is correlated with the loss in the ability to maintain integrity at the molecular biological level. Evolutionary-comparative analysis places an upper limit on the number of these systems important to the evolution of longevity in the primates, and suggests the importance of insuring the stability of information bearing macromolecules in evolution and the role of modulators of damage to these moieties in the expression of the senescent state  相似文献   
384.
385.
An analysis is made of alphafetoprotein (AFP) concentrations in 3630 amniotic fluids submitted for prospective prenatal diagnoses over a 7-year period. There were 89 cases of anencephaly, 74 of open spina bifida and 3467 with normal singleton outcomes. The AFP data were expressed in both standard deviations above the mean and multiples of the normal median for individual weeks of gestation. False positive and false negative rates were comparable in the two systems at selected cut-offs. It is concluded that either system may be used in setting action limits for the primary distinction of unaffected pregnancies from those in which an open neural tube defect is present.  相似文献   
386.
387.
388.
389.
390.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号